The effectiveness of illumination is usually affected by several factors, including light quantity & quality, contrast, amount of flicker, shadows, and intensity of glare. To optimize illumination in security, emergency, and safety situations, consider adjusting each factor differently. Lighting standards also play an important role in the design, installation, durability, and efficient distribution of illumination.
Measuring and stimulating Light Level – Illuminance
Illuminance is measured in foot candles (ftcd, fc, fcd) or lux (in the metric SI system). A foot candle is actually one lumen of light density per square foot; one lux is one lumen per square meter.
• 1 lux = 1 lumen / sq. meter = 0.0001 phot = 0.0929 foot candle (ftcd, fcd)
• 1 phot = 1 lumen / sq. centimeter = 10000 lumens / sq. meter = 10000 lux
• 1 foot candle (ftcd, fcd) = 1 lumen / sq. ft. = 10.752 lux
Calculating Illumination
Illumination is calculated using the formula = Ll Cu LLF / Al (1). In this formula, I denotes illumination (measured in lux, i.e. lumen per m2), Ll represents lumens/ lamp (i.e. lumen), Cu is the coefficient of utilization, while LLF is light loss factor and Al is the area/ lamp (measured in m2).
Light Planning: The Steps
Light planning is a five-step process. The actual process involves:
- Planning objective analysis
- Planning conditions analyses
- Overall planning
- Detailed planning
- Documentation
Understanding Glare
Glare can be categorized into two groups: discomfort and disability glare. The level of discomfort glare can be measured by determining the glare index in accordance to the UGR method. This is often graded on a scale, which ranges between 13 and 28 where the greater the glare index the greater the degree of glare. The smallest variation in the glare index designating a significant difference is three.
Reflections from reflective glare or materials can usually be avoided by adopting the following strategies:
· Choosing convenient luminaire positioning
· Using materials for all reflective surfaces
· Selecting fixture with effective screening and low luminous intensity
· Picking out luminaires with a bigger surface area
· Choosing light colors for your ceilings and walls
Balance is key
A well-balanced luminance is essential to boost visual clarity, effectiveness of the ocular functions of the eye, and contrast sensitivity. You should always avoid high luminance which can cause glare, intense luminance contrasts that may cause visual tiredness, and low luminance contrasts, which trigger a staid atmosphere that doesn’t stimulate.
Source (Copyright © 2018 Saving Light Bulbs)
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